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arXiv 1104.3829hep-ex
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在LHC上测量W ~+喷注事件中大横动量W玻色子的偏振

Measurement of the Polarization of W Bosons with Large Transverse Momenta in W+Jets Events at the LHC

CMS Collaboration

摘要:

首次测量了pp碰撞中大横动量W玻色子的偏振态。测量是基于36个反皮电子数的数据记录在sqrt(s)= 7 TeV的CMS检测器在LHC。本文用电子和μ子的衰变测量了横动量大于50 GeV的W玻色子的左手、右手和纵向极化率(fL,fR,f0)。μ子末态产生最精确的测量,(f_L - f_R)= 0.240 +/- 0.036(stat.)+/- 0.031(系统)f_0 = 0.183 +/- 0.087(stat.)+/- 0.123(系统)对于带负电荷的W玻色子,(f_L-f_R)= 0.310 +/- 0.036(stat.)+/- 0.017(系统)f_0 = 0.171 +/- 0.085(stat.)+/- 0.099(系统)带正电的W玻色子。这第一次证明了在具有大横动量的pp碰撞中产生的W玻色子主要是左手的,正如标准模型所预期的那样。

英文摘要:

A first measurement of the polarization of W bosons with large transverse momenta in pp collisions is presented. The measurement is based on 36 inverse picobarns of data recorded at sqrt(s) = 7 TeV by the CMS detector at the LHC. The left-handed, right-handed and longitudinal polarization fractions (f_L, f_R, f_0) of W bosons with transverse momenta larger than 50 GeV are determined using decays to both electrons and muons. The muon final state yields the most precise measurement, (f_L - f_R) = 0.240 +/- 0.036 (stat.) +/- 0.031 (syst.) and f_0 = 0.183 +/- 0.087 (stat.) +/- 0.123 (syst.) for negatively charged W bosons, and (f_L - f_R) = 0.310 +/- 0.036 (stat.) +/- 0.017 (syst.) and f_0 = 0.171 +/- 0.085 (stat.) +/- 0.099 (syst.) for positively charged W bosons. This establishes, for the first time, that W bosons produced in pp collisions with large transverse momenta are predominantly left-handed, as expected in the standard model.

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